Chassis for display backlight

Abstract

An electronic device may be provided with a display. Backlight structures may be used to provide backlight for the display. The backlight structures may include a light guide plate. A rectangular ring-shaped chassis may have a rectangular opening that receives the light guide plate. One or more edges of the chassis may be provided with an array of notches that receive light-emitting diodes or other light sources. The light sources may launch light into edge portions of the light guide plate. The chassis may include a first plastic structure such as a light reflecting structure formed from a material such as white plastic. The first plastic structure may surround two or more peripheral edges of the light guide plate. The chassis may also include a second plastic structure such as a light blocking structure formed from a material such as black plastic that helps prevent light leakage.

What is claimed is: 
     
       1. Backlight structures for an electronic device display, comprising:
 a rectangular light guide plate; 
 a light source that launches backlight into an edge surface of the rectangular light guide plate; and 
 a rectangular ring-shaped plastic chassis that surrounds the rectangular light guide plate, wherein the rectangular ring-shaped plastic chassis includes at least a first plastic structure and a second plastic structure formed from a different plastic material than the first plastic structure, wherein the second plastic structure forms an exterior surface of the rectangular ring-shaped plastic chassis that is parallel to the edge surface of the light guide plate, wherein the first plastic structure is interposed between the edge surface of the light guide plate and the second plastic structure that forms the exterior surface of the rectangular ring-shaped plastic chassis, wherein the first plastic structure extends noncontinuously around the rectangular light guide plate, and wherein a portion of the chassis opposite the light source is formed exclusively of material from the second plastic structure. 
 
     
     
       2. The backlight structures defined in  claim 1  wherein the first plastic structure is configured to form an inner surface along at least one interior edge of the rectangular ring-shaped plastic chassis. 
     
     
       3. The backlight structures defined in  claim 2  wherein the first plastic structure comprises white plastic. 
     
     
       4. The backlight structures defined in  claim 2  wherein the first plastic structure comprises a rectangular ring of light reflecting plastic. 
     
     
       5. The backlight structures defined in  claim 2  wherein the first plastic structure is configured to form a light reflecting surface along at least two sidewalls of the rectangular ring-shaped plastic chassis. 
     
     
       6. The backlight structures defined in  claim 5  wherein the second plastic structure comprises black plastic. 
     
     
       7. The backlight structures defined in  claim 6  wherein the first plastic structure comprises white plastic. 
     
     
       8. The backlight structures defined in  claim 5  wherein the chassis has first, second, third, and fourth edges, wherein the first and third edges are parallel, wherein the second and fourth edges are parallel, and wherein the first and third edges of the chassis are formed exclusively of material from the second plastic structure. 
     
     
       9. The backlight structures defined in  claim 5  wherein the chassis has first, second, third, and fourth edges, wherein the first and third edges are parallel, wherein the second and fourth edges are parallel, and wherein the first edge of the chassis is formed exclusively of the material from the second plastic structure. 
     
     
       10. The backlight structures defined in  claim 1  wherein the first plastic structure comprises light reflecting plastic, wherein the second plastic structure comprises light blocking plastic, wherein the light reflecting plastic is more reflective than the light blocking plastic, wherein at least some of the second plastic structure forms a sidewall portion of the rectangular ring-shaped chassis, and wherein at least some of the first plastic structure is located along an inner surface of the sidewall portion. 
     
     
       11. A backlight structure, comprising:
 a light guide plate having an edge surface that receives light from a light source; and 
 a chassis that surrounds the light guide plate, wherein the chassis includes a first injection molded plastic structure and a second injection molded plastic structure, wherein the first injection molded plastic structure forms an interior surface of the chassis, wherein the second injection molded plastic structure forms an exterior surface of the chassis, wherein the interior and exterior surfaces of the chassis are parallel to the edge surface of the light guide plate, wherein the interior surface is interposed between the edge surface of the light guide plate and the exterior surface of the chassis, wherein the second injection molded plastic structure completely surrounds the light guide plate, wherein the first injection molded plastic structure surrounds only a portion of the light guide plate, and wherein a portion of the light guide plate that is not surrounded by the first injection molded plastic structure is opposite the edge surface of the light guide plate that receives light from the light source. 
 
     
     
       12. The backlight structure defined in  claim 11  wherein the second injection molded plastic structure is more opaque than the first injection molded plastic structure and wherein the first injection molded plastic structure is injection molded on at least one peripheral edge of the light guide plate. 
     
     
       13. The backlight structure defined in  claim 12  wherein the first and second injection molded plastic structures are molded to each other along at least one edge. 
     
     
       14. The backlight structure defined in  claim 11  wherein the chassis has four edges, wherein the first injection molded plastic structure comprises white plastic, wherein the second injection molded plastic structure comprises black plastic, and wherein at least some of the black plastic surrounds each of the four edges of the chassis. 
     
     
       15. A backlight structure, comprising:
 a light guide plate having a peripheral edge surface; 
 a light source that emits light in to the peripheral edge surface of the light guide plate; and 
 a chassis that surrounds the light guide plate, wherein the chassis includes an outer structure and a metal coating on an interior surface of the outer structure, wherein the interior surface is parallel to the peripheral edge surface, wherein the metal coating is configured to reflect light into the light guide plate through the peripheral edge surface, and wherein the light emitted into the peripheral edge surface of the light guide plate is incident upon a portion of the interior surface of the outer structure opposite the peripheral edge surface into which the light source emits light. 
 
     
     
       16. The backlight structure defined in  claim 15  wherein the outer structure comprises plastic. 
     
     
       17. A backlight structure, comprising:
 a light guide plate having a peripheral edge surface; 
 a light source that emits light in to the peripheral edge surface of the light guide plate; and 
 a chassis that surrounds the light guide plate, wherein the chassis includes an outer light absorbing structure and a thin-film stack on an interior surface of the outer light absorbing structure, wherein the interior surface is parallel to the peripheral edge surface, wherein the thin-film stack is configured to reflect light into the light guide plate through the peripheral edge surface, and wherein the light emitted into the peripheral edge surface of the light guide plate is incident upon a portion of the interior surface of the outer light absorbing structure opposite the peripheral edge into which the light source emits light. 
 
     
     
       18. The backlight structure defined in  claim 17  wherein the thin-film stack includes a plurality of dielectric layers of differing indices of refraction. 
     
     
       19. The backlight structure defined in  claim 18  wherein the outer light absorbing structure comprises a ring-shaped structure formed from plastic.